Well tools



Nov. 9, 1965 w. w. DoLLlsoN 3,216,731

WELL TooLs Filed Feb. 12, 1962 2 sheets-sheet 1 Nov. 9, A1965 w. w.DoLLlsoN 3,216,731

WELL TOOLS Filed Feb. 12, 1962 2 sheets-sheet 2 22.5 so` @a7 183 227 202.INVENTOR F'Q- 2 william w.oo|||son ATTORNEYS United States Patent O3,216,731 WELL TOLS William W. Dollison, Dallas, Tex., assignor to OtisEngineering Corporation, Dallas, Tex., a corporation of Delaware FiledFeb. 12, 1962, Ser. No. 172,478 14 Claims. (Cl. 277-1) This inventionrelates to well tools and to methods relating to wells and moreparticularly to blow out preventers for preventing escape of well fluidsfrom a well during movement of a well flow conductor into or out of thewell and methods for preventing such blow outs of well uids.

An object of this invention is to provide a new and improved blow outpreventer for preventing blow out or escape of well fluids from a wellduring the movement of a well ilow conductor into or out of the wellwhich does not slow down the operation of pulling out or running in of awell flow conductor of a well.

Another object is to provide a blow out preventer having a plurality ofresilient elements engageable with a well flow conductor being run intoor pulled out of a well to prevent escape of well fluids from the wellduring such running or pulling operations wherein the pressure to whicheach of the sealing elements is subjected is relatively low and only afraction of the pressure of the well iluids whereby excessive wear ofthe resilient elements is avoided.

Another object is to provide a blow out preventer having a plurality ofspaced resilient elements which engage the well flow conductor toprevent escape of well fluids from the well as the well flow conductoris run into or pulled out of the well wherein the resilient sealingelements are subjected to approximately equal pressure diiierentialsthereacross with the pressure across each of the resilient elementsbeing a fraction of the pressure of the well iluids.

A further object is to provide a blow out preventer having a pluralityof resilient elements for engaging a well flow conductor being run intoor pulled out of a well having automatic means for maintaining thepressure dilerential across each of the sealing elements atpredetermined substantially constant values.

A still further object is to provide a blow out preventer having aplurality of low pressure sealing elements or strippers for engaging awell flow conductor being run into or pulled out of the well, each ofwhich is subjected to a predetermined low pressure diferential and whichcumulatively retain the high pressure well fluids within the well andprevent their escape out of the well during such running and pullingoperations.

Another object is to provide a blow out preventer having a plurality ofvertically spaced resilient elements engageable with the well flowconductor and having means for maintaining substantially constant equalpressure differentials across each of the sealing elements to hold thesealing elements in sealing engagement with the well flow conductorbeing run into or pulled out of the well, the pressure below each of theresilient elements being higher than the pressure below the nextresilient element positioned immediately thereabove.

Still another object of the invention is to provide a new and improvedmethod for preventing blow out or escape of well fluids from a wellduring running in or pulling out of a well flow conductor into or out ofa well by maintaining substantially constant pressure dillerentialsacross a plurality of longitudinally spaced sealing elements closing theannular space of the well about the well flow Conductor to hold thesealing elements in sealing engagement with the well ilow conductor withthe pressure lCe below each of the sealing elements being maintained ata value substantially higher than the pressure below the sealing elementspaced immediately thereabove.

Additional objects and advantages of the invention will be readilyapparent from the reading of the following description of a deviceconstructed in accordance with the invention, and reference to theaccompanying drawings thereof, wherein:

FIGURE 1 is a vertical sectional schematic illustration of a blow outpreventer of the invention usable to practice the method of theinvention mounted on a well head of a hydraulic snubbing apparatusemployed therewith for running in or pulling out a well ow conductor,such as a tubing string, into or out of the well;

FIGURE 2 is an enlarged vertical partly sectional view of the blow outpreventer;

FIGURE 3 is an enlarged sectional view of a pressure regulator of theblow out preventer of FIGURE 2;

FIGURE 4 is an enlarged sectional view of a pressure relief valve of theblow out preventer;

FIGURE 5 is a schematic illustration of the uid pressure system of theblow out preventer illustrated in FIG- URES 1 and 2 which employs thepressure of the well fluids to cause the sealing elements thereof toengage the well ilow conductor;

FIGURE 6 is a schematic illustration of another iluid pressure systemfor the blow out preventer which employs the pressure of the well iluidsfor the operation thereof;

FIGURE 7 is a schematic diagrammatic illustration of a lluid pressuresystem for operating the blow out preventer wherein an external sourceof iluid under pressure is employed; and,

FIGURE 8 is a schematic illustration of still another fluid pressuresystem for the blow out preventer which also employs an external sourceof uid under pressure.

Referring now particularly to FIGURES 1 through 5 of the drawing, theblow out preventers 10 and 11 embodying the invention are shownsupported on the well head 12. A snubber apparatus 15 is mounted on theupper preventer 11 for running in or pulling out a well ilow conductor,such as a tubing string T, formed of sections 16 connected by the usualcollars or couplings 17.

The snubber apparatus may be of any suitable type such as a snubberapparatus illustrated and described in the United Sates patentapplication, Serial No. 103,- 351, tiled April 17, 1961 by Phillip S.Sizer. The snubber apparatus may include a stationary snubber 18 havinga lower section 19 having slips 26 which are employed to hold the tubingstring against downward movement into the well and an upper section 21having slips 22 which are employed to hold the tubing string againstupward movement out of the well. The upper and lower sections of thestationary snubber are secured together in any suitable manner, as bythe bolts 24. The slips of the stationary snubber may be moved intotubing string engaging positions by any suitable means which are notdescribed in detail since they constitute no part of this invention.

The snubber apparatus 15 also includes a cylinder 27 having an internalcylindrical wall 28 to form an annular chamber C in which the annularpiston 29 is movable. The cylinder is secured to the upper section 21 ofthe stationary snubber 18 by any suitable means as by means of the bolts30. AA cylindrical piston rod 31 extends upwardly from the piston 29 andthrough a suitable annular yopening 32 in the top annular closure 33.Suitable seal means (not shown) of course are provided to seal betweenthe piston rod and the top closure 33. Conduits 35 and 36 communicatewith the upper i and lower portions 38 and 39 of the chamber so that byselectively admitting fluid under pressure into one portion andreleasing fluid for the other portion through these conduits, the pistonand the piston rod may be caused to move upwardly or downwardly asdesired.

A traveling snubber 42 is secured to the upper end of the piston rod 31and has slips 43 which are engageable with the tubing string. The meansfor operating the slips may be of any suitable type and have not beenshown since the snubber apparatus constitutes no portion of thisinvention.

In FIGURE 1, the traveling snubber 42 is shown in use for forcing thetubingT string T downwardly into the well against the pressure of thewell uids. It will be noted that the tubing string extends downwardlythrough the snubber 42, the cylindrical wall 28 of the snubberapparatus, the stationary snubber 18 and the blow out preventers 11 and10 into the well head 12 and thence into the bore of the well. Duringthe operations wherein the snubber 42 is in the position illustrated inFIGURE 1 and is being employed to force the tubing string downwardlyinto the well against the pressure exerted by the well uids, the slips43 of the traveling snubber 42 are caused to engage the tubing sectionwhile the piston is in its uppermost position and the slips 22 of theupper tubing section 21 are then moved to their retracted positions outof engagement with the tubing string. Fluid under pressure is thenintroduced into the upper portion 38 of the chamber C of the cylinder 27through the conduit 35, while the fluid in the lower portion 39 of thechamber C is allowed to escape through the conduit 36, to cause thepiston 29 to move downwardly and thus force the tubing string downwardlyinto the well. When the piston reaches the lower limit of its downwardtravel, the slips 22 of the upper stationary snubber 21 are caused toengage the tubing string to hold the tubing string against upwardmovement whereupon the slips 43 are moved out of engagement with thetubing string. The piston and the traveling snubber 42 are then movedupwardly to their initial upper positions by introducing fluid underpressure into the lower chamber 39 of the chamber C through the conduit36 while permitting the fluid in the upper portion 38 of the chamber Cto escape through the conduit 35. This cycle of operation can then berepeated so that the tubing string is moved incremently downwardly intothe well.

If the upper snubber is used to support the tubing string and controlits downward movement and if the weight of the tubing string issufficiently great to cause it to move downwardly by gravity, theposition of the traveling snubber is reversed so that the slips 43 willtend to grip and hold the tubing string against downward movementrelative to the snubber. The uid in the lower portion 39 of the chamberis then released 4at a controlled rate, While fluid is permitted toenter into the upper portion of the chamber 38 through the conduit 35,so that the tubing string is permitted to move at a controlled ratedownwardly into the well. When the piston and the traveling snubberreach the lower limits of their movement, the slips 20 of the lowersection 19 of the stationary snubber 18 are caused to engage the tubingstring to hold it against further downward movement. The slips 43 arethen moved out of engagement with the tubing string and fluid underpressure is introduced into the lower portion 39 of the chamber Cthrough the conduit 36, while the fluid in the upper portion 38 ispermitted to escape through the conduit 35, to move the travelingsnubber 42 back to its uppermost position whereupon the slips 43 thereofare again caused to engage the tubing string and the slips 20 are movedout of engagement with the tubing string so that this cycle of operationmay again be repeated to permit another length of the tubing string tomoved downwardly at a controlled rate into the well.

It will be apparent that the snubber apparatus may also be used to pullout the tubing string T or control its upward movement out of the wellin the event that the pressure of the fluids in the well is suicient toexpel the tubing string therefrom, in a similar way by the appropriateuse of the stationary and traveling sunbbers and by the controlled flowof fluids into and out of the upper and lower portioins of the chamberC.

During movement of the tubing string T into or out of the well, thelower and upper sealing elements or strippers a and 50h of the blow outpreventers 10 and 11 prevent blow out or escape of the wall fluids fromthe well. The lower blow out preventer 10 includes a tubular body orhead 51 having a longitudal bore 52 in which are disposed the resilientsealing elements 50a and 50b. The adjacent surfaces of the well head andthe head 51 are provided with aligned annular grooves 53a and 53b,respectively, in which are received lower and upper portions,respectively, of a seal ring 54 which seals therebetween. The head 51 isprovided with a lower external liange 5S which is secured to the flange56 of the well head 12 by means of bolts 57.

The lower sealing element 50a has an external retainer ring 59 at itsupper end portion, the resilient sealing element being moulded to theretainer ring. The sealing elements are tubular in form having a centrallongitudinal bore or passage 60 defined by the upper outwardly beveledor flared surface 61, a substantially cylindrical upper internal surface62, a downwardly and inwardly tapered surface 63, a cylindrical lowersurface 64 and a lower downwardly and outwardly beveled or ared surface65. The lower cylindrical surface 64 is of somewhat smaller diameterthan the external surface of the tubing section 16 so that resilientsealing element is in an expanded or stretched condition when a tubingsection 16 extends therethrough. The beveled upwardly facing surfaces 61and 63 act as cam surfaces to help guide the tubing string downwardlythrough the sealing element and the coupling 17 thereof to preventdamage to the resilient sealing element, and to cause progressivestretching or expansion of the resilient sealing elements as the tubingsections and the couplings move downwardly and approach the lowercylindrical surface 64 which delines the narrowest section of the flowpassage of the sealing element. The downwardly and outwardly beveled orflared surface 65 at the lower end of the sealing elements similarlyhelps to guide the tubing sections and the couplings upwardly to thecylindrical surface 64 of the sealing element and cause progressivestretching or expansion of the sealing element as the tubing string ismoved upwardly through the sealing element point. An annular downwardyextending external lip 66 intermediate the ends of the sealing elementis adapted to engage the internal surfaces of the head and sealthereagainst since upwardly acting uid pressure in the passage 52 willtend to expand the lip against the head.

The retainer ring has a downwardly facing shoulder 68 adapted to engagethe upwardly facing internal shoulder 69 provided in the passage 52 bythe enlarged upper portion 70 thereof. The retainer ring 59 also has anupper downwardly and outwardly beveled shoulder 72 which is engaged bythe lower annular similarly beveled shoulder 73 of a tubular adapter 75disposed in the enlarged upper portion 70 of the bore 52.

The sealing element 50b is identical in structure to the sealing element50a and components thereof have been provided with the same referencenumerals to which the subscript b has been added as the correspondingcomponents of the sealing element 50.

The retainer ring 59b of the upper sealing element 50h has itsdownwardly facing shoulder 68h engaging the upwardly facing shoulder 78of the adapter 75 which limits downward movement of the upper sealingelement in the head 51. The external annular lip 66b of the sealingelement Stlb engages the inner wall of the enlarged upper portion 70a ofthe bore 52a of the adapter. The lower and upper sealing elements 50aand Sb and the adapter are held against upward movement in the bore orpassage 52 of the head 51 above the shoulder 69 by a keeper ring 80releasably secured to the head by a split ring 81 whose inner and outerportions extend into aligned external and internal recesses 82 and 83 ofthe head and of the retainer ring, respectively. The split ring is heldagainst movement by the screws 84 which extend through suitableapertures of the keeper ring into threaded bores of the split ring. Abevel ring 85 has a downwardly and outwardly beveled shoulder 86 whichengages the upper shoulder 72b of the keeper ring 59h of the uppersealing element 5017 and an upper surface which engages the lowersurface of the split ring.

The adapter 75 is provided with a plurality of lateral apertures orports 90 which communicate with an external annular recess or groove 91thereof. The groove 91 is below a sealing means, such as an O-ring 93,disposed in a suitable annular recess of the adapter which seals betweenthe adapter and the head.

The head is provided with a lateral port 96 which communicates with theexternal annular recess 91 of the adapter head so that uid underpressure may be admitted into the chamber 97 within the adapter betweenthe lower and upper sealing elements.

Flow of fluid into the chamber 97 through the lateral port 96 of thehead is controlled by a pressure regulator Valve 100 which includes ahousing 101 threaded into the enlarged portion 102 of the lateral port96. A valve seat 104 has a reduced portion 105 which extends laterallyoutwardly into the bore 107 of the housing 101. The valve seat is heldin position in the port 96 by the engagement of the inner annularshoulder 108 of the housing 101 with the annular shoulder 110 of thevalve seat and the engagement of its annular end surface 111 with theshoulder 112 provided by the enlarged portion 102 of the port 96. Thevalve seat has an external annular recess in which a sealing means, suchas an O-ring 113b is disposed to seal between the head and the valveseat. The housing is provided with a similar sealing means, such as anO-ring 113:2 disposed in an external annular recess thereof which sealsbetween the head and the housing.

The valve seat 104 has a bore 114 through which extends the valve stem115 of the valve head 116 whose beveled shoulder 117 engages with theannular edge or shoulder 118 of the valve seat to close the bore 114 ofthe valve seat inwardly of the transverse flow passage 120 of the valveseat. The opposite ends of the transverse How passage open outwardlyinto the enlarged portion 102 of the port 96 and into an annular passageabout the valve head formed between seal means 113:1 and 113b. The valvehead 116 is baised toward engagement with the valve seat by a spring 121disposed about the valve stem whose opposite ends bear against the innerend surface of the reduced portion 105 of the valve seat and the washer123 disposed about the valve stem and held against outward movementthereon by a nut 124 threaded on the valve stem. It will be apparentthat the force with which the spring 121 biases the valve head towardengagement with the valve seat shoulder 118 may be adjusted by rotationof the adjusting nut 124 in one direction or another on the valve stem.

The head 51 of the blow out preventer is also provided with alongitudinal passage 126 whose upper end communicates with the enlargedportion 102 of the port 96 between the O-rings 113a and 113b and whoselower end intersects a lower transverse passage 128 of the head andopens downwardly of the head inwardly of the seal ring 54. The lowertransverse passage 128 of the head opens inwardly into the bore 52 belowthe lower sealing element 50a.

It will be apparent -that the uid in the bore 52 below the lower sealingelement A50a may ow upwardly through the longitudinal passage 126 to theenlarged portion 102 of the port 96, thence through the passage 120 andbore 114 of the valve seat 104 and through the lateral 6 port 96 of thehead into the bore 52 between the upper and lower sealing elements, andthen through the ports of the adapter into the chamber 97 under thecontrol of the pressure regulator valve 100. It will be apparent thatthe pressure regulator valve will maintain the pressure in the chamber97, when a tubing string extends through the lower blow out preventer,at a predetermined value which is lower than the pressure in the bore 52below the lower valve head. The pressure regulator valve opens wheneverthe pressure diferential between the chamber 97 and the bore 52 belowthe lower sealing element 50b rises above Value predeter-A mined by theadjusted position of the adjusting nut 124, it being apparent that thefluid pressure acting through the longitudinal passage 126 tends to movethe valve head towards its open position and the pressure within thechamber 97 tends to 4assist the valve spring 121 in biasing the valvehead towards its closed position.

The head 21 is also provided with a lateral port 130 which opens intothe bore or passage 52 of the head and communicates with the externalrecess 91 of the adapter head below the O-ring 93 thereof. The housing132 of a pressure relief valve 134 is threaded into the lateral bore130. The pressure relief valve 134 permits flow of fluids from thechamber 97 whenever the pressure within the chamber 97 exceeds apredetermined value. The pressure relief valve houisng has a passage 135which is closable by a valve body 137 whose rounded seat face 138 isengageable with the annular seat 139 of the housing. The valve |body 137has an enlarged spring retainer portion 140 provided with a recess 141in which is disposed a biasing spring 142 one of whose ends bearsagainst the shoulder 143 of the Valve and whose other end bears againstthe adjusting screw 144 threaded into the outer end of the housing. Thevalve body 137 may be provided with the passages 145 which communicatewith the interior of the spring retainer recess to facilitate flow ofuid through the housing when the valve body 137 is moved to openposition against the resistance of the spring 142. The adjusting screwhas an orice 148 through which the lluid may escape to the atmospherefrom the relief valve housing.

It will be apparent that the pressure relief valve is responsive to thepressure within the chamber 97 whenever such pressure exceeds apredetermined value. Rotation of the adjutsing screw 144 in onedirection or the other will of course change this predetermined value asdesired.

The head 51 is also provided with an upper lateral passage 150 whoseinner end opens into and communi- Cates with the bore 52 of the headabove the keeper ring 80 and the upper sealing element 50h and whoseouter end communicates with the lower transverse passage 128 through theconnector 151 which has a T fitting 152 threaded in the enlarged outerend portion 153 of the upper transverse passage, the conduit 155 whoseupper end is threaded into Vthe T connector 151, the pressure regulatorvalve 156 connected to the lower end of the conduit 155, T connector 157whose fitting 158 is received in the threaded enlarged portion 159 ofthe lower transverse passage 128, the pressure regulator valve 156 alsobeing connected to the T connector 157.

The T connectors are provided with the usual T- shaped flow passages151a and 157:1, respectively. The upper end of the conduit 155 isthreaded into one end of the connector 151 so that the upper end of itspassage 155a communicates with the passage 151:1 of the oon.- nector.The lower end of the conduit 155 is provided with an external annularange 160 which is secured to the upper end of the housing 162 by a cap163 threaded on the upper end of the housing. A sealing means, such asan O-ring 164, is disposed between the internal flange 165 of the capand the upper surface of the conduit flange 160 to seal therebetween anda sealing means, such as an O-ring 166, is disposed in an internalannular recess of the cap 163 to seal between the cap and the pressureregulator valve housing below the flange.

The pressure regulator valve 156 is identical in all other respects tothe pressure relief valve 134 illustrated in FIGURE 3, the housing 162being threadedly connected to the lower T connector 157 so that itspassage 168 is in communication with the T-shaped passage 157a of the Tconnector. The ow of fluid through the pressure regulator valve 156 iscontrolled by the valve lbody 170 having an arcuate -surface 171 of itslower end engageable with an annular valve seat 172 to close the owpassage 168. The valve body is biased toward closed position by thebiasing spring 175 whose lower portion is disposed in the recess 176 ofthe spring retainer portion 177 of the valve body with its lower endbearing against the upwardly facing shoulder 178 and its upper endbearing against the adjusting screw 180 threaded into the housing. Itwill be apparent therefore that the pressure regulator valve 156 willopen to permit uid to flow from the bore 52 of the head 10 bel-ow thelower sealing element 50a into the bore 52 above the keeper ringwhenever the pressure differential between the upper and lower portionsof tht bore 52 above and below the sealing elements exceeds a valuepredetermined by the position of the adjusting -screw 180.

A pressure relief valve 183, identical in all respects with the pressurerelief valve 134 is connected to the connector head 151 to permit flowof fluid from its passage 151a. The pressure relief valve 183 opens topermit escape of iluid from the bore 52 of the head above the uppersealing element 50h whenever the pressure at this point exceeds apredetermined value.

The upper blow out preventer 11 is substantially identical in allrespects to the lower blow out preventer having a body 200 secured tothe head 51 of the lower blow out preventer by means of the bolts 201which extend through suitable apertures in the lower external flange 202of the head 200 into suitable threaded bores in the upper externalflange of the lower head. A seal ring 204 whose lower and upper portionsare received in the aligned annular recesses or grooves 205 and 206 ofthe adjacent upper and lower surfaces of the two heads sealtherebetween. The upper flange 210 of the head 200 of the upper blow outpreventer is secured to the lower section 19 of the stationary snubber18 by means of bolts 211. A suitable sealing ring or gasket 212 hasupper and lower portions which are received in the aligned grooves 213and 214 of the head and of the snubber 19, respectively, to sealtherebetween.

The upper blow out preventer 11 has upper and lower sealing elements aand 50b which are held in spaced relationship by an adapter 75. Theassembly of the two sealing elements and the adapter is disposed betweenthe annular shoulder 216 of the head and the retainer ring secured tothe head by screws 84 in the same manner as are secured the sealingelements of the lower blow out preventer.

The head 200 has a lower transverse passage 220 similar to the lowertransverse passage 128 of the head 51 whose inner end does notcommunicate with the bore or passage 222 of the head 200 since its innerend is closed, in any suitable manner, as by a weld 223. Thelongitudinal passage 224 of the head 200 which corresponds to thelongitudinal passage 126 of the head 51, which intersects andcommunicates with the lower transverse passage 220, is closed by a weld225. One conduit 227, has one end threaded in the outer enlarged endportion of the transverse passage 220 and has its other end threaded ina suitable bore of an upper connector 228. The connector 228 has anL-shaped passage 229 which communicates with the bore 230 of the conduit227 and the bore 232 of a conduit 233 whose upper end is threaded in asuitable bore of the upper connector 228 and whose lower end is threadedinto a bore of a lower connector 234. The

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connector 234 has an L-shaped passage 235 which is in communication withthe bore 232 of the conduit 233 and also with the bore 237 of a fitting236 connected thereto. The tting 236 is threaded in a bore of the Tconnector 157 and its bore 235 is in communication with the passage 157aof the T connector and thus with the passage 128.

Flow of fluid from the bore 52 of the lower blow out preventer into thechamber 240 between the upper and lower sealing elements of the upperblow out preventer is controlled by a pressure regulator valve 242identical in all respects with the pressure regulator 100. The pressureregulator valve 242 is identical in structure with the pressureregulator valve 100 and, accordingly, the various components of thepressure regulator valve 242 have been provided with the same referencecharacters as the corresponding elements of the pressure regulator valve100.

The housing 101 of the pressure regulator valve 242 is threaded in theenlarged portion 244 of a lateral port of the head 200. The lateral portcommunicates with the chamber 240 and also with the upper end of thelongitudinal passage 224 of the head. The spring 121 of course holds thevalve head 116 in closed position preventing flow from the longitudinalpassage 224 into the valve of the head until the pressure differentialtherebetween exceeds a predetermined value.

The head 200 of the upper blow out preventer is also provided with alateral port 250 which communicates with the chamber 240 through theports of the adapter 75 and in whose threaded portion is secured apressure relief valve 252 whose structure is identical to that of thepressure relief valve 134. The components of the valve 252 are thereforeprovided with the same reference characters as the correspondingcomponents of the pressure relief valve 134. The pressure relief valve252, of course, prevents the pressure within the chamber 240 of the headfrom exceeding a predetermined Value. The head 200 has an uppertransverse passage 254 which however is plugged or closed by the plug255 in such installations as that illustrated in FIGURE l wherein onlytwo blow out preventers are employed.

In use, when the blow out preventers of the invention are employed toprevent the escape of well fluids from the well during movement of thewell flow conductor, such as tubing string T, into or out of the well,and if, for example, the pressure of the well fluids is ten thousandpounds per square inch, the pressure regulator valve is adjusted byrotation of its nut 124 so that it will open whenever the pressuredifferential between the bore 52 of the lower blow out preventer belowthe lower sealing element 50a and the chamber 97 between the two sealingelements thereof exceeds two thousand tive hundred pounds per squareinch. As a result whenever the pressure within the chamber 97 dropsbelow seven thousand five hundred pounds per square inch, the pressureregulator valve 100 will open to permit the flow of well uids into thechamber 97 until the pressure in the chamber 97 is again raised to seventhousand ve hundred pounds per square inch. The relief valve 134 isadjusted to open whenever the pressure in the chamber 97 rises apredetermined degree above seven thousand tive hundred pounds per squareinch, say to seven thousand ve hundred fifty pounds per square inch, sothat the pressure within the chamber 97 will not fall below seventhousand tive hundred pounds per square inch and will not rise aboveseven thousand five hundred fifty pounds per square inch. As a result,the pressure differential across the lower sealing element never exceedsa predetermined value, in this case approximately two thousand tivehundred pounds per square inch.

The pressure regulator valve 156 is adjusted to open whenever thepressure differential between the bore 52 of the lower head below thelower sealing element 50a and the chamber 260 formed by the two heads ofthe two blow out preventers and between the sealing element 50b of thelower blow out preventer and the sealing element 50a of the upper blowout preventer exceeds fve thousand pounds per square inch. The pressurerelief valve 183 is adjusted to open at a value slightly higher thanfive thousand pounds per square inch, say ve thousand fty pounds persquare inch, so that the pressure within the intermediate chamber 260 isheld within the range of five thousand pounds per square inch to livethousand fifty pounds per square inch. It will thus be apparent that theupper sealing element 50h of the lower blow out preventer is subjectedto a pressure differential of approximately two thousand five hundredpounds since the pressure in the chamber 97 of the lower blow outpreventer is maintained at approximately seven thousand five hundredpounds per square inch.

The pressure regulator valve 242 is similarly adjusted to open wheneverthe pressure differential between the bore 52 of the lower blow outpreventer below the lower sealing element 50a thereof and the chamber240 of the upper blow out preventer exceeds seven thousand five hundredpounds per square inch so that the pressure regulator valve 242 -willopen whenever the pressure within the chamber 240 drops below twothousand five hundred pounds per square inch. The pressure relief valve252 is adjusted to open at a value slightly higher than two thousandfive hundred pounds per square inch, say two thousand five hundred fiftypounds per square inch, so that the pressure within the chamber 249 isheld within the range of two thousand five hundred pounds per squareinch and two thousand five hundred fifty pounds per square inch.

It will now be seen that each or" the sealing elements of the lower andupper blow out preventers and 11 is held in sealing engagement with thetubing string which extends therethrough by a pressure differential ofapproximately two thousand five hundred pounds per square inch so thatthe full pressure of ten thousand pounds per square inch of the wellfluids is in eflect staged across the sealing elements of the blow outpreventers and no sealing element is subjected to pressure differentialsgreater than approximately t-wo thousand five hundred pounds per squareinch as the tubing string is moved either downwardly or upwardly throughthe blow out preventers by a suitable snubber apparatus, such as thesnubber apparatus illustrated in FIGURE l.

The pressure Within each of the chambers 240, 250 and 97 tends to risesharply each time a coupling 17 moves thereinto because the movement ofa coupling into a chamber reduces the volume of the chamber. Thepressure within each chamber however remains substantially constantsince the pressure relief valves 252, 183 and 134 allow the escape offluid from each chamber as the couplings pass thereinto to prevent thepressure therein from exceeding the predetermined value. As thecouplings move out of the chambers, the pressure within the chamberstends to drop since the volumes of the chambers now increase. However,as the pressure in each chamber drops below the predetermined value, thepressure differential between such chamber and the bore 52 of the head51 increases since the pressure of the well fluids remains substantiallyconstant and the appropriate pressure regulator valve 100, 156 or 242opens to permit ilow of the well fluids into such chamber until thepressure within such chamber again attains the desired predeterminedvalue.

It will now be seen that a new and improved blow out preventer forpreventing escape of well fluids from a well during the movement of awell flow conductor into or out of the well has been illustrated anddescribed which includes a tubular member or head connectible to thewell head and having its bore in longitudinal alignment with the bore ofthe well, the tubular member being provided with `a plurality ofresilient sealing elements which seal between the well llow conductorand such tubular member or head, the blow out preventer having means forregulating the pressure differential across each of the sealing elementsso that the fluid pressure below each sealing element is greater thanthe pressure immediately thereabove and so that each sealing element issubjected to a pressure differential which is much smaller than thepressure differential bet-Ween the atmosphere and the well fluids andbears only a portion of the force exerted by the pressure of the wellfluids tending to llow between the well flow conductor and the tubularmember.

It will further be seen that the means for subjecting the sealingelements of the blow out preventer to a predetermined pressurediferential includes pressure regulator valves for admitting fluid underpressure into the tubular member between adjacent spaced sealingelements of the blow out preventer to maintain the pressure differentialacross such sealing elements at predetermined values and with reliefvalves for preventing the pressure between adjacent ends of adjacentsealing elements from exceeding predetermined Values.

It will be apparent that the well flow conductor, such as a tubingstring having externally extending couplings or collars 17, may be movedcontinuously through the sealing elements of the blow out preventerswithout the necessity of stopping movement of the tubing string eachtime a coupling is moved through the blow out preventer as is necessarywhere conventional ram type blow out preventers are used.

It will further be seen that the blow out preventer includes a headhaving a pair of resilient sealing elements 50a and 50h which are heldin longitudinally spaced positions by adapter 75 to provide a chamberbetween the sealing elements, that fluid under pressure is admitted intothe chamber through a pressure regulator valve and that lluid is allowedto escape from the chamber through a pressure relief valve so that thepressure .within such chamber is maintained at a substantially constantpredetermined value.

It will further be seen that the pressure relief Valves permit escape offluid from the chamber as the volume of the chamber is decreased by thepassage of a tubing string thereinto to prevent the pressure thereinfrom increasing above predetermined value and that the pressureregulator valves permit flow of fluids into such chamber as the volumeof the chamber is increased upon the movement of a coupling or collar 17out of the chamber to prevent the pressure therein 4from falling below apredetermined value,

It will now be seen that the method of the invention for preventing blowout or escape of well fluids from a well during movement therethrough ofa well flow conductor which may or may not have spaced external annularflanges, such as couplings, includes disposing a plurality oflongitudinally spaced sealing elements about the -well flow conductor toengage the well flow conductor to close the annular space thereabout andto form chambers between adjacent yends of adjacent sealing elements andabout the well flow conductor, introducing fluid pressure into thechambers to create a predetermined pressure diflerential across each ofthe sealing elements tending to hold the sealing element in sealingengagement with the well flow conductor, and maintaining the pressurewithin each chamber at a predetermined value which is lower than thepressure to which is subjected the lower end of the sealing elementdefining the lower end of the chamber.

The method also includes the step of permitting lluid to escape fromeach chamber as an external flange of the well flow conductor entersinto such chamber and decreases the volume of the chamber to prevent thepressure within the chamber from exceeding a predetermined value and thestep of permitting fluid under pressure to enter each chamber as anexternal flange leaves the chamber to prevent the pressure within thechamber from falling below a predetermined value.

.pounds per square inch.

If desired, as indicated in broken lines in FIGURE 5, accumulators 266,267 and 263 may be connected to the blow out preventers in such mannerthat they are placed in communication with the chambers 240, 260 and 37,respectively, in order to minimize the llow of iluids through thepressure regulator valves and the pressure relief valves. Each.accumulator may be in the form of a closed container, a portion at leastof which is lllled with a compressible gas so that fluid lfrom each ofthe chambers of the blow out preventers will tend to flow into itsassociated accumulator thus further compressing the gas in theaccumulator as a coupling enters into such chamber and reduces itsvolume and will flow therefrom and into its associated chamber as thecollar of the well flow conductor moves out of such chamber and thusincreases its volume. In this manner the llow of fluid through thepressure regulator and pressure relief valves is minimized which may bedesirable where the well lluids contain sand, mud or other abrasiveswhich tend to damage the seating surfaces of such valves.

It will be apparent that when the pressure regulator valves 100, 156 and242, as shown in FIGURES 1, 2 and 5, are connected in parallel with thebore 52 of the head 51 of the lower blow out preventer 10 below thelower sealing element 50a thereof, the pressure regulator valve 242 mustregulate the flow of fluids when subjected to a higher pressuredifferential than the other two pressure regulator valves and that thepressure regulator valve 100 must regulate the flow of fluids when it issubjected to a predetermined but lower pressure differential than theother two pressure regulator valves. If desired, the pressure regulatorvalves may be connected in series, as illustrated schematically inFIGURE 6, to the source of fluid pressure in order that each of thepressure regulator valves may be subjected to the same pressuredifferential. It will be noted that the pressure regulator valve 100 isconnected between the bore 52 of the lower head 51 below the lowersealing element 50a of the lower blow out preventer and the chamber 97thereof between its upper and lower sealing elements so that thepressure on the upstream side of the pressure regulator 100 in the givencase is ten thousand pounds per square inch and the pressure on thedownstream side is approximately seven thousand five hundred pounds persquare inch. The pressure regulator valve 100 is then subjected to apressure differential of approximately two thousand five hundred Thepressure regulator valve 156 has its inlet end in communication with thedownstream or outlet end of the pressure regulator valve 100 while itsdownstream or outlet end is connected to the chamber 260 between thelower and upper sealing ele- `ments of the upper and lower blow outpreventers and per square inch. The pressure regulator valve 242 has itsupstream or inlet end connected to the downstream or outlet end of thepressure regulator valve 156 and its downstream or outlet end connectedto the chamber 240 of the upper blow out preventer 11 so that itsupstream end is subjected to a pressure of lve thousand pounds persquare inch and its downstream end is subjected to a pressure of twothousand tive hundred pounds per square inch. This pressure regulatorvalve, like the other two pressure regulator valves, is thus subjectedto a pressure differential of approximately two thousand five hundredpounds per square inch. It will thus be seen that the pressure regulatorvalves when connected in series as illustrated in FIGURE 6 are eachsubjected to equal pressure differentials. The relief valves 134, 183and 252 are of course adjusted to open at some value slightly higherthan seven thousand five hundred pounds per square inch,

ve thousand pounds per square inch, and two thousand five hundred poundsper square inch, respectively.

In the event that the well iluids contain excessive amounts of sand, mudor other abrasives or are highly corrosive, the chambers 97, 260 and 240between the sealing elements of the blow out preventers 10 and 11 may beprovided with clean fluids under pressure from an external source 275which may be another well producing relatively clean fluids or which maybe a hydraulic pump. In this event, the lower transverse passage 128 ofthe head 51 of the lower blow out preventer would be provided with anexternal plug 276, similar to the plug 255 illustrated in FIGURE 2, toclose the outer end of the lower transverse passage 128 while the innerend of the transverse passage 128 is closed in the sa-me manner as thelower transverse passage 220 of the upper blow out preventer 11 isclosed by the weld 223. The lower end of the longitudinal passage 126 ofthe head 51 of the lower blow out preventer is also closed at its lowerend in the same manner that the longitudinal passage 224 of the head 200of the upper blow out preventer 11 is closed by the weld 225. As shownin FIGURE 7, the external source of fluid under pressure is connected tothe chambers between adjacent sealing elements of the blow outpreventers with the pressure regulator valves thereof connected inseries.

It will be apaprent of course that the pressure .regulator valves couldbe connected in parallel between the chambers and the external source oflluid under pressure as is shown in FIGURE 8 wherein the hydraulic pump300 is employed as the source of fluid under pressure. The drive shaft301 of the pump 300 is driven by any suitable prime mover such as anelectric motor (not shown). The inlet duct 303 of the pump extends andopens into a reservoir tank 304 of the liquid which is to be deliveredto the chambers 97, 260 and 240 formed by the two blow out preventersthrough the regulator valves and 156 and 242, respectively. The outletconduit 305 of the pump 300, which has a check valve 307 connectedtherein to prevent reverse flow of iluid therethrough is connected tothe conduit 308 whose parallel branches 311, 312 and 313 are connectedto the inlet ends of the pressure regulator valves 100, 156 and 242. Apressure accumulator 315 may be connected in communication with theconduit 305 between the pressure regulator valves and the check valve307. The pressure accumulator has at least a portion thereof lllled withcompressible gas. An overload dump valve 318 may be connected by meansof the conduits 319 and 320 across the outlet and inlet conduits 305 and303, respectively, of the pump 300. The overload dump valve is providedwith a biasing spring 322 which biases the overload dump valve 318towards closed position. The conduit 323 transmits the pressure of thefluid in the outlet line 305 to the overload dump valve to cause it toopen whenever the pressure in the outlet line exceeds a predeterminedvalue.

In operation, the xed displacement pump 300, when initially placed inOperation, pumps the liquid from the tank 304 and the regulator Valveswill permit tlow of the liquid into the chambers of the blow outpreventers until the pressure differential across each of the pressureregulator valves attains a predetermined Value and the pressureaccumulator is filled with liquid to a predetermined degree and heldunder a predetermined pressure by the thus compressed gas of theaccumulator. When the pressure within the pressure accumulator 315attains a predetermined value, the overload dump valve 31S opens sincesuch pressure is transmitted thereto by the conduit 323. The pump 300may therefore continue to operate even though no further fluid ispermitted to tlow past the check valve 307 and merely recirculates thefluid between its inlet and outlet conduits 303 and 305. Should thepressure within one of the chambers 97, 260 or 240 now drop to increasethe pressure differential across one of the pressure regulator valves,such valve opens and permits Huid to flow into such chamber causing ythepressure within the conduit 305 to drop. VThis drop in pressure causesthe pressure overload dump valve 318 to close and the pump will nowcause iluid under pressure to ow through the check valve 307 to thepressure accumulator and to such chambers of the blow out preventerthrough the regulator valves.

While the outlet conduit 305 of the pump has been shown as connected tothe conduit 308 whose parallel branches are connected to the regulatorvalves, it will be apparent that the outlet conduit 305 of the pump 300could be connected to the upstream or inlet end of the pressureregulator valve 100 of the circuit as illustrated in FIGURE 7 whereinthe pressure regulator valves are connected in series. It will now beseen that the pump 300 may be employed as the external source of fluidpressure for the blow out preventers.

The pressure of the well fluids may be of such value that only twosealing elements are necessary. For example, if each sealing elementoperates satisfactorily under a pressure dilerential thereacross of twothousand ive hundred pounds per square inch and the pressure of the wellfluids does not exceed five thousand pounds per square inch, only thelower blow out preventer 10 would be employed. In this case, the lowerand upper transverse passages 128 and 150 of the head 51 would be closedto the outside by suitable plugs, such as the plug 255. The pressureregulator valve 100 would be adjusted to open when the pressurediierential thereacross increased above two thousand ive hundred poundsper square inch. The pressure regulator valve 134 would be set to openat a somewhat higher pressure, say two thousand five hundred twenty-livepounds per square inch. As la. result, the pressure differential acrossthe lower sealing element 50a would be maintained at approximately twothousand live hundred pounds per square inch since the pressureimmediately therebelow would be ve thousand pounds per square inch andthe pressure immediately thereabove in the chamber 97 would beapproximately,

two thousand tive hundred pounds per square inch. Similarly, the uppersealing element 50a would be subjected to a pressure diierential ofapproximately two thousand live hundred pounds per square inch since thepressure in the chamber 97 is maintained at approximately two thousandfive hundred pounds per square inch and the upper end thereof is nowexposed to the atmosphere since the upper blow out preventer 11 is notpresent.

It will be apparent that as many of the blow out preventers, connectedserially one to another in longitudinal alignment, may be employed asdesired depending upon the pressure of the well fluids and the pressuredifferential to which the individual sealing elements may be subjectedwithout causing undue wear or deterioration of the sealing elements.

It will now be seen that a new and improved blow out preventer has beenillustrated and described which employs any desired number oflongitudinally aligned and spaced sealing elements in a tubular memberwhich is placed in longitudinal alignment and in communication with thewell, so that a well ow conductor may be moved through the sealingelements with the sealing elements sealing between the tubular memberand the well flow conductor and that the tubular member may be composedof any number of the heads or sections.

It will further be seen that each of the sealing elements is subjectedonly to a fraction of the total pressure differential between theatmosphere and the well bore so that a plurality of sealing elements,each one of which is capable of satisfactorily resisting only a smallpressure differential thereacross, may be employed to prevent blow outof the well fluids.

It will further be seen that the low conductor may be moved continuouslythrough the sealing elements without the necessity of arresting itsmovement each time an enlarged portion of the well ow conductor, such asthe labor when the blow out preventers embodying the invention areemployed.

The foregoing description of the invention is explanatory only, andchanges in the details of the construction illustrated may be made bythose skilled in the art, within the scope of the appended claims,without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A well tool including: a tubular member having a bore; a plurality oftubular sealing elements disposed in said tubular member inlongitudinally spaced relation, said sealing elements being engageablewith an elongate member movable through said tubular member and sealingtherebetween to provide a plurality of longitudinally spaced chambersbetween each adjacent pair of sealing elements; and means providing forflow of fluid from the bore of the tubular member at a point upstream ofone end sealing element exteriorly of the sealing elements and back intothe tubular member into the chambers between said sealing means, saidlast mentioned means including pressure regulator means for maintainingthe pressure in each successive chamber at a pressure reduced by apredetermined amount below the pressure in the chamber next upstreamtherefrom.

2. A well tool of the character set forth in claim 1 wherein, saidpressure regulator means includes pressure regulator valve meanscontrolling admission of fluid pressure to each of said chambers forpreventing the pressure in each of said chambers between said sealingelements from decreasing below a predetermined value; and fluid pressureresponsive release means for preventing the pressure in each of saidchambers between said sealing elements from exceeding said predeterminedvalue.

3. A well tool for preventing escape of well uids from a well duringmovement of an elongate member into or out of the well including: atubular member installable on the well and having a longitudinal passagein longitudinal alignment with the well bore; a plurality of tubularsealing elements disposed in said tubular member in longitudinallyspaced alignment, said sealing elements being enga geable with anelongate member movable through the tubular member for sealingtherebetween, said tubular member, said elongate member and said sealingelements providing annular chambers between adjacent ends of adjacent:sealing elements; tluid pressure responsive regulating means forconducting fluid under pressure at predetermined reduced values fromupstream of each of said sealing elements into the chamber between saidsealing element and the next downstream sealing element; and fluidpressure responsive means communicating with the chamber betweenadjacent pairs of said .sealing elements for releasing uid pressure fromsaid chamber when the pressure within the chamber exceeds apredetermined value, whereby a predetermined pressure reduction ismaintained across each sealing element of the plurality of sealingelements decreasing in value from the most upstream sealing element tothe most downstream sealing element.

4. A well tool for preventing escape of well lluids from a well duringmovement of an elongate member into or out of the well including: atubular member installable on the well and having a longitudinal passagein longitudinal alignment with the well bore; a plurality of tubularsealing elements disposed in said tubular member in longitudinallyspaced alignment, said sealing elements being engageable with anelongate member movable through the tubular member for sealingtherebetween, said tubular member, said elongate member and said sealingelements providing annular chambers between adjacent ends of adjacentsealing elements; fluid pressure responsive regulating means forintroducing fluid under pressure from upstream of each of said sealingelements into the chamber between said sealing element and the sealingelement next downstream thereof at a predetermined reduced lowerpressure, whereby the pressure in the chambers between each of saidsealing elements is introduced at a predetermined reduced value from theupstream to the downstream side of such lsealing elements in each ofsaid chambers; and pressure responsive means for releasing fluid fromeach of said chamber when the pressure within the chamber exceeds apredetermined value. 5. A well tool for preventing escape of Well fluidsfrom a Well during movement of an elongate member into or out of thewell including: a tubular member installable on the well and having alongitudinal passage in longitudinal alignment with the well bore; aplurality of tubular sealing elements disposed in said tubular member inlongitudinally spaced alignment, said sealing elements being engageablewith an elongate member movable through the tubular member for sealingtherebetween, said tubular member, said elongate member and said sealingelements providing annular chambers between adjacent pairs of sealingelements; and means connectable to a source of fluid under pressure forintroducing fluid under pressure into said chambers at a predeteminedvalue in each of said chambers whenever the pressure within saidchambers falls below said predetermined values, including means formaintaining the pressure in each of said chambers at a predeterminedlower value than the pressure in the chamber next upstream, whereby thepressure across each of said sealing elements is reduced by apredetermined amount from upstream to downstream thereof.

6. A well tool for preventing escape of well fluids from a well duringmovement of an elongate member into or out of the well including: atubular member installable on the well and having a longitudinal passagein longitudinal alignement with the well bore; a plurality of tubularsealing elements disposed in said tubular member in longitudinallyspaced alignment, said sealing elements being engageable with anelongate member movable through the tubular member for sealingtherebetween; said tubular member, said elongate member and said sealingelements providing annular chambers between adjacent ends of adjacentsealing elem-ents; and means connectable to a source of luid underpressure for introducing fluid under pressure into each of said chambersat a value reduced by a predetermined amount below the pressure in thechamber next upstream therebelow when the pressure within each of saidchambers falls below said predetermined values, said predeterminedpressure in each of said chambers being maintained at a lower value thanthe pressure in the next lower chamber; and fluid pressure responsivemeans for releasing fluid from each of said chambers when the pressurewithin the chamber exceeds a predetermined value.

7. The method of preventing escape of fluids from a well during movementof an elongate member into or out of the wall including: disposing atubular member having a longitudinal passage with a pair oflongitudinally spaced tubular sealing elements therein in longitudinalalignment with the well, moving the elongate member through thelongitudinal passage, and introducing lluid pressure from the well boreupstream of the lowermost chamber successively; into each annularchamber thereabove between adjacent sealing elements defined by saidsealing elements, the tubular member and the elongate member to maintaina successively lower predetermined pressure differential acrosssuccessive sealing elements tending to hold the sealing elements insealing engagement with the elongate member and the tubular member; andmaintaining the pressure within each chamber at a predetermined valuewhich is lower than the value of the pressure in the chamber next below.

8. The method of preventing escape of iluids from a We duri-Hg movmellof an elongate member into or out of the well including: disposing atubular member having a longitudinal passage with a pair oflongitudinally spaced tubular sealing elements therein in longitudinalalignment with the well, moving the elongate member through thelongitudinal passage, and introducing fluid pressure into an annularchamber between adjacent sealing elements defined by said sealingelements, the tubular member and the elongate member to maintain apredetermined successively lower pressure differential across the4sealing elements from the lowermost to the uppermost of said elementstending to hold the sealing elements in sealing engagement with theelongate member and the tubular member; permitting fluid to escape fromthe chamber whenever the volume of the chamber decreases and an enlargedportion of the elongate member moves into the chamber to prevent thepressure differential across of the lower sealing element fromdecreasing below a predetermined value, and permitting fluid to flowinto the chamber as the volume of the chamber increases as an enlargedportion of the elongate members moves out of the chamber to prevent thepressure differential across the lower sealing element from increasingabove a predetermined value.

9. The well tool of claim 5, wherein said means for maintaining fluidunder pressure of predetermined value in each of said chambers includespressure regulator valves, each of said pressure regulator valvesregulating introduction of iluid into an associated chamber.

10. The well tool of claim 9, wherein said pressure regulator valves areconnected in series to said source of fluid under pressure.

11. The well tool of claim 9, wherein said pressure regulator valves areconnected in parallel to said source of fluid under pressure.

12. The well tool of claim 5, and pressure accumulator means connectedto each of said chambers for minimizing flow of iluid into said chamber.

13. The well tool of claim 6, and pressure accumulator means connectedto each of said chambers for minimizing flow of fluid into and out ofsaid chambers.

14. A well tool for preventing the escape of well fluids from a wellduring movement of an elongate member into and out of the wellincluding: a tubular member installable on the well and having alongitudinal passage in longitudinal alignment with the well bore; aplurality of tubular sealing elements disposed in said tubular member inlongitudinally spaced alignment therein, said sealing elements beingengageable with an elongate member movable through the tubular memberfor sealing therebetween, said tubular member, said elongate member andsaid sealing elements providing a plurality of longitudinally spacedannular chambers in said tubular member between adjacent ends ofadjacent sealing elements, the volume of the chamber between adjacentsealing elements varying as portions of said elongate member ofdifferent external diameter are moved therethrough; and fluid pressureresponsive means for controlling the pressure of fluid introduced intothe chambers between said elements and maintaining said pressures insaid chambers at predetermined fixed successively lower values from thelowermost chamber to the uppermost chamber.

References Cited by the Examiner UNITED STATES PATENTS 528,773 11/94Ellis 277-3 728,124 5/03 Mitchell 277-3 2,080,715 5/37 Hinderliter 277-62,155,837 4/39 Penick et al. 277-6 2,908,515 10/59 Schellens 277-33,145,995 8/ 64 Adamson et al. 277-28 EDWARD V. BENHAM, Examiner.

LEWIS I. LENNY, Primary Examiner,

1. A WELL TOOL INCLUDING: A TUBULAR MEMBER HAVING A BORE; A PLURALITY OFTUBULAR SEALING ELEMENTS DISPOSED ON SAID TUBULAR MEMBER INLONGITUDINALLY SPACED RELATION, SAID SEALING ELEMENTS BEING ENGAGEABLEWITH AN ELONGATE MEMBER MOVABLE THROUGH SAID TUBULAR MEMBER AND SEALINGTHEREBETWEEN TO PROVIDE A PLURALITY OF LONGITUDINALLY SPACED CHAMBERSBETWEEN EACH ADJACENT PAIR OF SEALING ELEMENTS; AND MEANS PROVIDING FORFLOW OF FLUID FROM THE BORE OF THE TUBULAR MEMBER AT A POINT UPSTREAM OFONE END SEALING ELEMENT EXTERIORLY OF THE SEALING ELEMENTS AND BACK INTOTHE TUBULAR MEMBER INTO THE CHAMBERS BETWEEN SAID SEALING MEANS, SAIDLAST MENTIONED MEANS IN-